1. Field of the Invention
The present invention relates to a method and a device for deflecting wire-rod strand moving at high speed.
2. Description of the Prior Art
It is known that during the mill process, wire-rod traveling through a mill train is cropped or separated either to improve the conditions of entering downstream mill stands, or to separate lengths of rod which do not meet the quality requirements and discard such lengths as scrap.
The cropping or separating of wire-rod strand is carried out by means of so-called flying shears. Such flying shears operate at extremely high revolutions per minute. See EP 297,313 B1 and DE 3,523,046 A1 patents. Such shears, however, represent highly complicated mechanical systems. Due to the high product speeds, the shear blades and the switch components are subjected to rapid mechanical wear. At product speeds of more than 80 m/s, such a system can only be controlled with sophisticated electronic equipment. In addition, the switch systems have to be located at considerable distance away from any cutting and sorting device so as to account for the switching delay.
Furthermore, it is known to guide the wire-rod strand by means of switches to downstream machines, or to feed cropped ends to suitable scrap disposal means. The switches are driven by means of hydraulic cylinders, pneumatic cylinders, moving screws, electric motors, or by a combination of such devices. As mentioned above, the greatest problem of the switch systems is the need for a short switching time particularly at high product speeds. Typically, the switching time is less than 1/10 of a second.
An additional device for deflecting the wire-rod strand is a deflector flap. This device, however, has several drawbacks. First, direct contact of the product with the guiding means may cause the wire-rod strand to break out of the guides at high product speeds. Moreover, direct contact may result in damage to the product. Such a disadvantageous guiding system for deflecting the wire-rod strand was disclosed in DE 3,523,046, where the guiding system is brought into contact with the product in order to guide the latter into appropriate guide runners.
In order to avoid the drawbacks outlined above, foreign patent DD 145,503 deflects the wire-rod product by applying a force to the latter by means of an external magnetic field surrounding the product. Such a magnetic field is generated by a magnet coil of a suitably selected size, and a current flowing through the product. The drawback of this design is that considerable technical means are required for generating the magnetic field. In addition, the magnetic field in the magnet coil is not very strong due to the large dimensions of the coil and the relatively large spacing from the magnetic field of the wire-rod strand. Another disadvantage results from the application of current to the magnetic coil and the product via sliding contacts. Such a configuration results in rapid wear especially at high product speeds. Furthermore, it is not clear how the wire-rod strand is to be held against the sliding contacts. Consequently, such a configuration is only suitable for a limited number of applications.